The invention relates to a plastic part as described herein. A plastic part of this kind is known (German Offenlagungsschrift 21 20 175). In this known realization, the metal threaded element has protrusions which have the plastic of the plastic part cast or sprayed over them circumferentially. In this manner, a tight connection is created which is resistent to conventional stresses in terms of stability. However, if for any reason, such as a soiled or damaged thread, the stress during twisting is too great, then the connection is excessively stretched or the threads are stripped. The connection is no longer tight and the plastic part is destroyed. During assembly, the stripping of the thread may go unnoticed; if the plastic part is a cover for a brake valve, for instance, the leakage thus arising can cause severe problems in the brake system.